1. Field of the Invention
The invention relates to a phase shifter, and more particularly to a full range phase shifter.
2. Description of the Related Art
With the proliferation of wireless communication, the demands on antennas have increased. A single antenna typically has only a fixed field. To fulfill practical demands, antennas are generally designed to have full range. A full range design provides convenience. An adjustable field antenna offers increased data rate and relatively better communication capability under interference and high noise. A full range antenna can be achieved by building an antenna array comprising several antennas and a phase shifter. The field of the antenna array is made changeable by utilizing the phase shifter at the backend of the antennas for adjusting the phases of input or output signals. Various phase-array antennas such as the core technique, smart antenna, multiple-input multiple-output (MIMO) system, and adaptive antenna system (AAS) are inspired to fulfill the demands of high data rate, wide coverage, and channel capacity.
The smart antenna, to be adopted by the 4th generation communication system, can process signals received from the antenna array; thus, the field of the antenna array is adjusted automatically. The beam-forming capability of the phase-array antenna offers the gain and focused coverage required by services such as WiMax.
In phase-array antenna systems and the described smart antenna, phase shifters play a key role. A phase shifter can be analog or digital depending on the phase shifting method. The analog phase shifter can be a reflective load phase shifter, a transmission line load phase shifter, or an inductor and capacitor phase shifter. The digital phase shifter can be a vector sum phase shifter and a line switch phase shifter.